This invention relates to improved well drilling apparatus of a type adapted to eliminate the necessity for a rotary table, kelly or kelly bushing.
Conventional rotary drilling as practiced for many years has required the use of a rotary table containing an opening through which a noncircular kelly pipe extends for engagement with a kelly bushing mounted in the table, in a relation driving the kelly bushing and connected drill string rotatively while permitting downward advancement of the kelly relative to the table. Alternative drilling systems have been proposed in which the drive to the pipe string has been derived from a drilling unit including a section of pipe connectable to the upper end of the drill string, and a motor for driving that pipe rotatively to turn the string. This entire powered drilling assembly may then move upwardly and downwardly with the string to drive the string very directly and positively and without the necessity for a kelly and kelly bushing type connection.